trying to figure out why my car is surging and....

[ninobrn99]

Im trying to figure out why my car is surging really bad at 2k on down and why its eating up so much gas! The car was tuned by Sean Freese at Fastech in Jan.
About a month later I noticed the car wasnt running right after I took it to the track. My friend hooked it up to his EFI and noticed that the LTFt's were 25+ at idle and about 16 or so at cruising speeds. I thought I found the problem------the intake manifold didnt have any oring gaskets. The car is still eating gas really bad! I ended up getting new o2 sensors from autozone. they helped a little, but went bad quick, so i replaced them under warrenty and still not doing to well. I got a used set of stock o2s and the car was running a bit better, but my LTFT's are 20+ onbank 1 and about 16+ on bank 2. The rears are deleted. at about 2700 rpm they're at 9.4+ bank 1 and 16.4 bank 2 ( about the same at idle-875) when i let off the gas the ltft's go back into the +20's.
I have a 228/228 5.76 114, LT's ory, tr55's ls6 intake, stock plug wires and heads. Can someone give me a few ideas on what to check to help fix this one of few problems? Let me know what other info you need.
Thanks,
Nino

[MNR-0]

You need to take it back and get a retune for part throttle and revise your fuel trims. It has leaned off, a common occurrence with Speed Density. The surging you are talking about has got to do with the IAC stepper motor unable to control the off-idle and return-to-idle conditions. This has to do with Idle tuning (things like Base Runing Airflow, Throttle Follower and Throttle Cracker) and quite possibly the fact you are running too lean when coming to a stop (again, fuel trims).

Just needs a bit more time to get it right. Good luck.

[ninobrn99]

Well I can tune it with Tuners. What do you suggest that I adjust? Ve tables? add fuel? relace something? Ive done everything I can think of mechanically and think that its all the tune that needs to be done. My friend has done a few things with tuners with the injectors to try to lower the trims, but didnt help too much. Plugs show that the car is running lean, but clean.

[MNR-0]

Are you running SD or MAF?

First thing is to bring your trims into line. If MAF, you can alter the MAF cal. or the IFRs. If SD, yo got to use the VE table. After that, there's a wealth of data here on idle tuning. Log your STITs and LTITs and move from there, getting the running airflow right. Then, move on the part throttle decel. stuff and tailor the Cracker and Follower to suit.

[ninobrn99]

Im keeping it MAF'd. Ill have my friend look into it. Thanks alot!!!